Vmware Player is slow under Ubuntu 16 host

So you just upgraded your Ubuntu box and found that all your VmWare Windows Boxes are extremely slow?

The symptom is your Windows task manager showning 100% usage of your disk, and the WIndows Instrumentation showing very long lags, says, up to 2.5seconds (yes, seconds) to respond to a disk request. This makes the box practically unusable.

But for some (obscure) reason, it doesn't work anymore. Again, a (this time) long search will point you to the correct answer: this post suggests to check another variable if you are using closed sources drivers for Nvidia, __GL_SYNC_TO_VBLANK=0.

Indeed this worked very well. I don't know why it changed, I suspect that the Ubuntu upgrader silently changed from open source to closed source drivers. Perhaps I tried them and when I switched to Open Source drivers, something remained. Really, I don't know, if someone has the response, please share it.

Now my Windows Boxes are fast enough to be used; now I have to deal with Windows Updates, but this is yet another story.